1. Field of the Invention
The present invention relates to a slot machine which includes a plurality of video reel strips.
2. Description of the Background Art
Conventionally, as a slot machine including a plurality of video reel strips, for example, there is a model which has the below-mentioned technology. In the technology which such a model has, since a game is subsequently initiated by the occurrence of triggering, the plurality of video reel strips are upgraded. When the plurality of video reel strips are upgraded, it becomes easy for a player to obtain a winning combination (for example, refer to US patent application publication 2012/0172106).
However, as a method of upgrading the plurality of video reel strips, for example, a method in which the number of wild symbols which can be substituted with any symbols is increased is adopted. Then, since it is easy for a player to recognize the increase in the number of the wild symbols, a player can soon perceive that the plurality of video reel strips have been upgraded.
Accordingly, a new design for upgrading the plurality of video reel strips has been desired by players.
Therefore, in view of the above-described respect, the present invention was made. An object of the present invention is to provide a slot machine which realizes a new design for upgrading the plurality of video reel strips.